Collisional energy transfer in optically pumped far-infrared lasers

A numerical simulation of collisional energy transfer in optically pumped far-infrared (OPFIR) lasers is presented along with a discussion of each collisional process and how it affects laser operation. A simulation is required to adequately describe these lasers because of the relatively large number of nonequilibrium states and thermal pools that are significant in the dynamics of their excitation and relaxation. The results of diagnostic studies and theoretical considerations are used to restrict the numbers of degrees of freedom so that a numerically tractable and physically satisfying model results. The resulting simulation accurately characterizes collisional energy transfer in these lasers over a much wider range of physical conditions than is possible with analytic models. These conditions include the very low pressure regimes most suited to the recovery of fundamental molecular collisional energy transfer parameters. Significantly for OPFIR laers, it predicts a new operating regime, which has been experimentally verified, that leads to small, tunable CW laser systems.